I am in combat, and the dialog box with "end turn" and "end combat" buttons (usually present at the lower right of the main window) is not present.

I suspect it's a bug.

By the way, I am playing the gametap version, so I can't update any files.

Anyone else encounter this?

Any help appreciated.

Few things. This may be a "monkey" (which is designed to stop you from playing the game after a certain point/time) Or you may have changed something in settings, best thing to do is to change the settings back, save and reload the game.